Treatment of aluminum alloys

ABSTRACT

S NEW SLUMINUM ALLOY COMPOSED OF FROM 0.01 TO 0.8 PERCENT EACH OF MAGNESIUM AND IRON, FROM 0.001 TO0.3 PERCENT OF BERYLLIUM, AND A REMAINDER OF ALUMINUM AND IMPURITIES. THIS ALLOY CAN BE CAUSED TO EXHIBIT EFFECTIVELY ITS EXCELLENT PRPERTIES BY TREATING IT AS THE BERYLLIUM THEREIN IS MAINTAINED IN A SOLID-SOLUTION STATE AND PREVENTED FROM PRECIPITATION.

United States Patent O 3,823,041 TREATMENT OF ALUMINUM ALLOYS Kazuo Tazaki and Toshiro Kobayashi, Kawasaki, Japan,

assignors to Fuji Denki Seizo Kabushiki Kaisha, Kauagawa-ken, Japan No Drawing. Original application Jan. 27, 1971, Ser. No. 110,331, now abandoned. Divided and this application Apr. 26, 1972, Ser. No. 247,870

Claims priority, application Japan, Feb. 10, 1970, 45/ 11,726; July 24, 1970, 45/ 64,880 Int. Cl. C22f 1 04 US. Cl. 148-2 5 Claims ABSTRACT OF THE DISCLOSURE This application is a divisional of our copending, application Ser. No. 110,331 filed Ian. 27, 1971, now abandoned.

BACKGROUND OF THE INVENTION This invention relates generally to the metallurgy of aluminum alloys and more particularly to a series of novel alloys containing aluminum as the basic constituent and,

having highly desirable characteristics, particularly for utilization as materials for electrical conductors and magnet wires. The invention further relates to a new process for treating these novel alloys whereby their desirable characteristics are exhibited with maximum effectiveness.

Heretofore, alloys of heat-treatable type such as Aldrey and AA6201 have been known particularly as aluminum alloys for electrical conductor of high mechanical strength. Alloys of this heat-treatable type, however, require a large number of process steps and entail much labor and high costs in their production.

On the other hand, alloys such as the so-called AA5005 alloy of the aluminum-magnesium series, which are known as those of the work-hardening type, are not accompanied by the disadvantages of the heat-treatable alloys but tend to be deficient in electroconductivity and heat resistance.

Furthermore, aluminum-zirconium alloys are well known as alloys possessing excellent heat resistance but have considerably low mechanical strength.

Attempts have been made to compensate for the disadvantageous features of the above mentioned alloys and to provide alloys possessing simultaneously various desirable properties, one proposed alloy being an alloy of aluminum, magnesium, and a rare-earth element. However, even this alloy is not fully satisfactory on the points of heat resistance and electroconductivity.

SUMMARY OF THE INVENTION ties which are all excellent.

Another object of the invention is to provide a new process for treating the aluminum alloys thereby to en I hance theabove stated excellent properties thereof.

According to the present invention in one aspect thereof, briefly summarized, there is provided a series of aluminum alloys each comprising, in percentage by weight, from 0.01 to 0.8 percent of magnesium (Mg), from 0.01

Patented July 9, 1974 more clearly apparent from the following detailed description beginning with a consideration of general features of the invention and concluding with specific examples constituting preferred embodiments of the invention and results.

DETAILED DESCRIPTION While a novel aluminum alloy according to the invention is made by adding respectively specific quantities of magnesium, iron, and beryllium to the aluminum metal, the quantities of these elements added dilfer depending on the quantities thereof originally contained in the base metal aluminum as impurities.

The additive components of each aluminum alloy according to the invention may be considered to function in an interrelated manner to achieve the objective eifect, provided that additive quantities are within their respective ranges stated.

We have found that when the magnesium content is less than 0.01 percent, the effectiveness thereof with respect to the mechanical strength and heat resistance of the alloy is not detectable. On he other hand, when the magnesium content is above 0.8 percent, the electroconductivity of the alloy is lowered to an extent which gives rise to problems in practice. When the iron content is below 0.01 percent, there is no appreciable effect thereof in improving the mechanical strength and heat resistance of the alloy, while an iron content greater than 0.8 percent gives rise to a lowering particularly of the electroconductivity and corrosion resistance. A beryllium content less than 0.001 percent does not have much effect in improving the heat resistance and the electroconductivity, while a beryllium content above 0.3 percent results in a saturation of its effect and, moreover, is economically disadvantageous.

By using the additive elements in the alloys in quantities within their respective ranges as specified above according to the invention, alloys possessing the aforementioned excellent properties can be produced and advantageously used as magnet wires for use in various electrical machines and equipment and as power-transmission wires and other conductors.

In order to indicate more fully the nature and utility of the invention, the following specific examples of aluminum alloys according to this invention are set forth and compared with known aluminum alloys of like class, it being understood that these examples are presented as illustrative only, and that they are not intended to limit the scope of the invention.

Example 1 comprising continuous casting and rolling. Samples thus formed of each alloy was subjected to tests for electroconductivity and tensile strengths at room temperature after different heating processes. The results are shown in Table 2.

4 Example 2 A known aluminum for electrical use (EC Al), a

known alloy of aluminum, magnesium, and a rare-earth element (Al-Mg-Re alloy), an alloy of aluminum, magneusim, iron, nickel, and beryllium (Al-Mg-Fe-Ni-Be TABLE 1 alloy) previously invented and proposed by us, and an al- Added element loy (Al-Mg-Fe-Be alloy) of this invention of the alloycentby weight mg composition set forth in Table 1 were subjected to Sample number Alloy Mg Fe Be casting, hot rolling at the temperature of solidification as the temperature dropped after casting similarly as in 1 Al-Fe-Be 0.30 0.010

0,019 Example 1, and cold working into fiat-type, or rectangua 0.14 0.31

Invention alloy (1).... 0.14 0.30 0.003 l 9 4 x 10 We (wipercem cold Work 5 0.15 0.31 0.010 mg after intermediate annealing). 1-" 8% 8-38 3- The wire samples thus produced were then subjected s: 0115 0120 0.020 to heatcycles and mechanical stress considered to be 9 Invenm (119 simulating those the wires would be subjected to in actual TABLE 2 use as transformer windings. The samples were then subjected to various tests, whereupon the results as indicated Tenslle gfl g at in Table 4 were obtained. In addition, corrosion tests were carried out on the samples specified in Table 3, and the Elcctw ME; results indicated in Table 5 were obtained. In carrying S I b condue- Origins} 0; 0., 2 0x 0" out these tests, the surface conditions of all samples were er mate made uniform, and the tests were carried out at 20 de- 23-2 0-1 12-1 3-3 we 58:5 101g 25 TABLE 3 10. 22.3 10. 5 14. 0 12. 0 Added n p ce y 59. 2 10. e 14. 2 13. weleht Sample No. Metal Mg Fe Ni Be Re 1 1 58 3 20 0 15 0 E- lngextiion Al alloy 0.14 0.31 0. 000 From th esult f these t t i i apparent h t b I I: sl-M it 1113;013:3311307175111333:12233133311232 bining and adding magnesium and iron in the alloys of 14 Al Mg Fe NlBe alloy" TABLE 4 Test condition H AfterheatinglOOhours Alter repeated stress (Condltlon before test) at 100 0. test Measurement temperature Room temp. 150 0. 150 0. 150 C.

Measurement Conduc- Tensile Elon- Tensile Eion- Tensile Elon- Tensile Elon- Sample tivity strength gation strength gation strength gation strength gatiou number (percent) (kg/mm (percent) (kg/mm!) (percent) (kg/mm!) (percent) (kgJmmJ') (percent) 50.0 16.0 0.5 14.7 3.1 13.2 8.3 12.0 10.8 62.6 12.4 0.0 11.2 8.1 10.2 8.4 0.7 0.4 50.8 15.8 0. 3 14. 1 7.8 11.8 8.8 11. e 6.0 50.3 17.1 8.9 15.5 6.7 13.2 as 14.1 s. 2

Repeated stress test: Each sample after heating for 100 hrs. at 200 C. was subjected to cycles of repeated stress ol 0 kgJmm.

this invention, the mechanical strength and heat resistance are improved without a great lowering in the electroconductivity. It is further apparent that as the added quantity of beryllium increases, it improves the electroconductivity and, moreover, the heat resistance of the alloy. However, when this beryllium added quantity reaches a value of about 0.3 percent, the effect thereof in improving the heat resistance tends to assume a saturation state.

It appears that these excellent characteristics of the alloys of this invention are obtainable because the additive elements such as iron and beryllium assume a solidsolution state more readily in a continuous casting and rolling process than in a conventional hot-rolling process, whereby each of these additive elements function etfectively. Therefore, iron in a quantity of the order of that already existing as an impurity in the aluminum for electrical use is further added in accordance with the invention thereby to increase the iron quantity and increase the etfect of improving the properties of the alloy.

The addition of beryllium, in addition to improving the properties of the product as set forth hereinbefore, also has the advantage of contributing to improvements such as that of castability and melting yield and is advantageous in the case of difficult casting processes such as a continuous casting and rolling process.

From the foregoing description, it will be apparent that each of the aluminum alloys of this invention possesses simultaneously mechanical strength, heat resistance, conductivity, and corrosion resistance, whereby they are highly suitable for use as materials for magnetic wires in electrical machines and equipment, particularly those for operation at high temperatures, and as materials for conductors for electrical power transmission and distribution.

While beryllium is a highly effective alloying element, excessive heating in the production of an aluminum alloy containing beryllium will cause separation of the beryllium, whereby the benefit obtainable thereby will be lost until, finally, the heat resistance of the alloy will drop. We have found that, by compulsorily causing this beryllium to assume the solid solution as much as possible, the conductivity of the alloy is further improved, and the heat resistance of the alloy is also improved.

A number of processes for producing an alloy of this invention composed of 0.15 percent of magnesium, 0.31 percent of iron, 0.009 percent of beryllium, and a remainder of aluminum are indicated as examples in Table 6. Certain properties of alloy samples produced by these production processes are set forth in Table 7.

TABLE 6 Sample number Production process 11 Casting and continuous rolling immediately after solidflcation (continuous casting-rolling method).

12 Cold rolling.

13 350 C. X30 min. ingot heating, then hot rolling (hot rolling method).

14 450 0. X2 hr. ingot heating, then hot rolling (hot rolling method).

15 Hot rolling, 550 0. X1 hr. solution treatment, then cold rolling.

No'rE.-Total worked rate of Samples 11 through 14 was 67%; that oi Sample 15 was 95%.

Recrystallization temperature is herein defined as that temperature at which the hardness of the sample assumes a value just intermediate ggigrveen that at room temperature and that when heated at 500 C. for one From the foregoing example, it will be apparent that, in the production of an aluminum alloy containing beryllium -by the ordinary hot-rolling method, an alloy simultaneously possessing excellent heat resistance and high electroconductivity can be obtained by reducing heating steps to a minimum and compulsorily rendering beryllium into a solid solution state thereby to prevent precipitation thereof.

One mode of practice of this production method on an industrial scale is the continuous casting-rolling process, wherein the alloy is cast and, immediately upon solidifying, is rolled by utilizing its high temperature as mentioned in Table 6 for Sample 11. Furthermore, in the ordinary hot-rolling process wherein an ingot is reheated and rolled, it is also possible to carry out a heating and rolling process at a temperature below 400 de r es C. in relation with the process time. In the particular case where the beryllium separates out during the production, it is desirable to carry out a solution treatment with respect to beryllium.

We claim:

1. A process for treating an aluminum alloy consisting essentially of by weight, from 0.01 to 0.8 percent of magnesium, from 0.01 to 0.8 percent of iron, from 0.001 to 0.3 percent of beryllium, and a remainder of aluminum and impurities which comprises rolling the alloyat a temperature at which said beryllium is maintained in a state of solid-solution and precipitation thereof is substantially prevented.

2. A process for treating an aluminum alloy containing beryllium according to Claim 1 in which the beryllium is maintained in the solid-solution state by casting the alloy and, immediately after solidification thereof, rolling the same by utilizing the elevated temperature thereof.

3. A process for treating an aluminum alloy containing beryllium according to Claim 1 in which the beryllium is maintained in the solid solution state by heating an ingot of the alloy at a temperature below 400 degrees C. and rolling the same.

4. A process for treating an aluminum alloy containing beryllium according to Claim 1 in which the beryllium is rendered into the solid-solution state by subjecting the alloy to a rolling process and to a solution heat treatment at a temperature in the range of from 500 to 650 degrees C. at an intermediate time during said rolling process.

5. A process for treating an aluminum alloy containing beryllium according to Claim 1 in which the beryllium is rendered into the solid-solution state by subjecting the alloy to a rolling process and to a solution heat treatment at a temperature in the range of from 500 to 650 degrees C. after said rolling process.

References Cited UNITED STATES PATENTS 1,751,468 3/ 1930 Archer 148159 1,952,049 3/1934 Archer et al. -147 US. Cl. X.R.

RICHARD O. DEAN, Primary Examiner 

